中国南极考察航线上气旋大风过程统计分析

A statistical analysis on cyclonic gale processes along Chinese Antarctic Research Expedition routes

综合使用“雪龙”号走航气象观测数据、SeaSpace极轨卫星云图、ERA-Interim再分析数据,研究了中国第19~34次南极考察航线上由南大洋气旋导致的气旋大风过程,分析了其发生数量及时间间隔、强度和空间分布等特征,探讨了气旋大风发生间隔与南极涛动的关系。南大洋气旋对中国南极考察航线影响频繁且强烈,气旋大风过程数量与航次时长呈显著正相关,平均而言每个航次出现约18(4)次气旋大风过程(强过程),平均每间隔6.5(30)天就出现一次;气旋大风过程中,过程风速平均达8级,最大可达12级。但气旋大风过程的数量、发生时间间隔、最大风速都存在较为明显的航次差异。气旋大风过程时间间隔与南半球夏季南极涛动指数呈负相关,且对于发生在55°S以南的过程负相关更为显著;南极涛动通过调整中高纬度风压带强弱,并影响气旋活动数量和活动区域,进而影响考察航线上气旋大风过程发生数量和频率。气旋大风过程可以发生在南大洋和极区内的任意航段,其中以45°~60°S绕极西风带内发生最为频繁,尤其易出现在气旋中心及其北侧与副热带高压配合产生的强梯度风区内。在4个重点考察海域中,由于阿蒙森低压的存在,阿蒙森海气旋大风过程和强过程发生最为频繁,其次是南极半岛海域,而普里兹湾和罗斯海气旋大风过程频率明显低于前两个海域,由于罗斯海最为偏南,不易受到气旋大风过程影响。

Using the meteorological observation data and SeaSpace polar-orbiting satellite images collected on the R/V Xuelong, in conjunction with the ERA-Interim reanalysis data, this paper studies the cyclonic gale processes(CGPs) that occurred in the 19 th to 34 th Chinese Antarctic Research Expedition(CHINARE-Antarctic). The characteristics of the number, occurrence interval, intensity, and spatial distribution are analyzed statistically. And the relationship between occurrence interval of CGPs and the Antarctic Oscillation(AAO) is discussed. The Southern Ocean cyclones have frequent and strong impacts on the CHINARE-Antarctic routes. A significant positive correlation can be seen between CGPs number and the time duration of voyages. On average, there are about 18(4) CGPs(strong ones) per voyage, which occurs once every 6.5(30) days, and the average wind speed during CGPs reaches Beaufort wind scale 8, while the maximum of which can reach scale 12. However, the number, occurrence interval and maximum wind speed of CGPs vary significantly during different voyages. There is a negative correlation between the occurrence interval of CGPs and the austral summer AAO index, which is significant for the CGPs appeared over the poleward side of 55°S. AAO adjusts the strength of the mid-high latitude pressure regime and affects the number and active area of cyclone activities, which in turn affects the number and frequency of CGPs. The CGPs can occur in any segment of the Southern Ocean and Polar Region, with the most frequent occurrence over the circumpolar westerly in 45°~60°S, especially in the strong pressure gradient zone produced by the combination of the low-pressure system and the northern subtropical high. In the four key expedition areas around Antarctica,the CGP and strong CGP over the Amundsen Sea occur most frequently because of the strong Amundsen Sea Low,followed by the Antarctic Peninsula, while the Prydz Bay and Ross Sea CGPs are significantly lower than the former two regions. Compared with the Prydz Bay, the Ross Sea is less susceptible to cyclones due to its southernmost position.